Scottish Labour Leader Kezia Dugdale will today call for a constitutional convention to “re-establish the UK for a new age”.
The MSP will accuse the Conservatives of having put the Union at risk in a speech in London.
And she will call for the UK to follow where Scotland led in the 1980s and 1990s.
Ms Dugdale is expected to say: “The convention should bring together groups to deliberate on the future of our country and propose a way forward that strengthens the UK and establishes a new political settlement for the whole of our country.
“This is a convention that the UK Government should convene, and I have written to Theresa May today outlining Scottish Labour’s desire to see this happen.”
But she will also insist that if the Tories are not willing, the Opposition should convene it.
She will add: “The time has come for the rest of the UK to follow where Scotland led in the 1980s and 1990s and establish a People’s Constitutional Convention to re-establish the UK for a new age.
“Some may say this is unrealistic, but it would follow the model of the Scottish Constitutional Convention which, without government support, established the basis for the settlement that delivered a Scottish Parliament in 1999.
“It would also – for the first time – provide a coherent approach to answering the question of how our country is best governed.
“While devolution has been positive for Scotland, Wales and Northern Ireland, we have to acknowledge that progress has been erratic and while there has been significant progress in some parts of the UK, other parts have been left behind.”
Ms Dugdale will set out her plans in a speech to the Institute for Public Policy Research (IPPR) think tank.